Consider the solution to the bounded buffer producer/consumer problem by using general semaphores S, F, and E. The semap...

Question

Consider the solution to the bounded buffer producer/consumer problem by using general semaphores S, F, and E. The semaphore S is the mutual exclusion semaphore initialized to 1. The semaphore F corresponds to the number of free slots in the buffer and is initialized to N. The semaphore E corresponds to the number of elements in the buffer and is initialized to 0.

Producer Process:
  Produce an item;
  Wait(F);
  Wait(S);
  Append the item to the buffer;
  Signal(S);
  Signal(E);

Consumer Process:
  Wait(E);
  Wait(S);
  Remove an item from the buffer;
  Signal(S);
  Signal(F);
  Consume the item;

Which of the following interchange operations in a process may result in a deadlock?
  I.   Interchanging Wait(F) and Wait(S) in the Producer process
  II.  Interchanging Signal(S) and Signal(F) in the Consumer process

A. (i) only
B. (ii) only
C. Neither (i) nor (ii)
D. Both (i) and (ii)

Accepted Answer

Only interchange (i) causes a deadlock. Answer: A. (i) only This problem involves a bounded buffer shared between a producer and a consumer, synchronized using three semaphores: S (mutex), F (free slots), and E (filled slots). We need to check which re-ordering of Wait/Signal calls can cause a circular wait (deadlock). A deadlock happens when the producer and consumer each hold a semaphore that the other needs.